The present invention relates to a process for preparing 7-hydroxy-1,2-naphthoquinone-2-diazide-4-sulfonic acid or salts thereof. These compounds may be used in the preparation of light-sensitive compounds and radiation-sensitive mixtures.
Esters, amides and hydrazides of 1,2-naphthoquinone-2-diazide-sulfonic acids have been used for many years as light-sensitive compounds for radiation-sensitive mixtures such as, for instance, photoresists for the production of semiconductor components in microelectronics or as coating solutions for the production of photomechanically processable printing forms or color proofing films. Suitable compounds and processing methods have been described in J. Kosar, Light-Sensitive Systems, John Wiley & Sons, New York, Chapter 7.4, 1965, U.S. Pat. No. 4,104,070, U.S. Pat. No. 4,576,901 and EP 0,212,482.
The preparation of the 1,2-naphthoquinone-2-diazide-sulfonic acids on which these known derivatives are based starts from 1-naphthol-4-sulfonic acid or 1-naphthol-5-sulfonic acid. The starting material is nitrosated with an alkali metal nitrite in dilute mineral acid. The 2-nitroso-1-naphthol-sulfonic acids formed are isolated, and the unconverted starting materials as well as the by-products formed during the nitrosation are removed by washing out or redissolution. The nitroso compound is then reduced in aqueous solution to the corresponding amino compound The latter is isolated and freed of unconverted starting materials, and of by-products formed, by digestion in water or by redissolution. The amino compound is then suspended in water and diazotized at a pH of 4-6 with an alkali metal nitrite in the presence of Cu(II) salts. In most cases, the 1,2-naphthoquinone-2-diazide-sulfonic acids obtained in this way must still be freed by redissolution or recrystallization from the dark-colored by-products formed in the diazotization.
The disadvantage of this preparation process is essentially that the starting materials unconverted in the individual reaction stages and the by-products formed must be separated from the desired main product by an additional purification step. This entails low yields, a not always satisfactory product quality and high production costs.
EP 0,283,898 discloses a process for preparing benzoquinone-diazide-sulfonic acids and naphthoquinone-diazide-sulfonic acids, which may be substituted by halogen, nitro groups or alkyl groups, and salts thereof. In this case, the starting material is an arylsulfonic acid having at least one hydroxyl group, the acid is nitrosated in a known manner, the nitroso compound formed is reduced in the alkaline pH range and the amino compound is then converted to a sulfamate derivative which is subsequently mixed with a diazotizing agent. After acidification of the mixture, this gives the benzoquinone-diazide-sulfonic acids or naphthoquinone-diazide-sulfonic acids. The reaction products formed after each reaction step are not isolated in between but remain in solution for further reaction ("one-pot reaction"). By-products and impurities arising in the individual process steps can be removed in a satisfactory manner by filtration of the reaction solution.
It is disadvantageous in this one-stage process that the various process steps can be carried out only within a relatively narrow pH range and the reaction times and reaction temperatures must be adhered to very exactly. The end products obtained by this process are as a rule not free of isomeric compounds. A universal industrial use of the compounds prepared by this process is therefore restricted.
In German Patent Application P 38 37 499.4, which is not a prior publication, a process for the preparation of esters of ring-substituted 1,2-naphthoquinone-2-diazide-4-sulfonic acids is described, wherein 1,2-naphthoquinone-2-diazide-4-sulfonic acids, substituted in the 5-, 6-, 7- or 8-position by halogen, alkoxy or alkoxycarbonyl, arise as intermediates.
In this case, the starting material is a correspondingly substituted 2-naphthol which is nitrosated in the 1-position, the product is sulfonated with alkali metal hydrogen sulfite in the 4-position, and the nitroso group is then reduced at a pH of about 7 or less by acidification with a mineral acid to give the amino group. The 2-amino-1-naphthol-4-sulfonic acid is oxidized to the corresponding 1,2-naphthoquinone-4-sulfonic acid, and the latter is reacted with p-toluenesulfonic acid hydrazide in an organic solvent at temperatures of 20.degree.-100.degree. C. to give the corresponding ring-substituted 1,2-naphthoquinone-2-diazide-4-sulfonic acid.
By means of chlorination with chlorosulfonic acid or a chlorosulfonic acid/thionyl chloride mixture, the sulfonic acid chloride is obtained in a known manner, and this is then condensed with a phenolic component to give the corresponding ring-substituted 1,2-naphthoquinone-2-diazide-4-sulfonic acid esters. The individual process steps for preparing the intermediates and end products are known from the literature. The process is dependent on the relatively poor accessibility of the substituted 2-naphthols used as the starting materials. For example, 7-alkoxy-2-naphthol is obtained according to known processes by monoalkylation of 2,7-dihydroxynaphthalene in a yield of only about 50-55% of theory. The yields of the subsequent reaction stages--nitrosation, sulfonation and reduction, oxidation, introduction of the diazo group - are satisfactory. In spite of the omission of additional purification of the intermediate stages, the overall yield of 7-alkoxy-1,2-naphthoquinone-2-diazide-4-sulfonic acid, relative to the 2,7-dihydroxynaphthalene employed, is not yet satisfactory, so that the production costs for the sulfonic acid esters which can be prepared are relatively high.
A further process for preparing ring-substituted 1,2-naphthoquinone-2-diazide-4-sulfonic acids, which can be used for the synthesis of the corresponding esters and amides, is indicated in German Patent Application P 38 37 500.1, which is not a prior publication. For the preparation of 7-methoxy-1,2-naphthoquinone-2-diazide-4-sulfonic acid, the starting material is, for example, commercially-available 1-acetylamino-7-naphthol. The latter can be converted in a 7-stage reaction sequence - methylation of the phenolic hydroxyl group, elimination of the acetyl group and preparation of 1-amino-7-methoxynaphthalene hydrogen sulfate, sulfonation in the 4-position by dry heating ("baking reaction"), replacement of the amino group by a hydroxyl group ("Bucherer reaction"), nitrosation in the 2-position, reduction of the nitroso group to the amino group, and diazotization to the desired compound.
Because of the multi-stage nature of the process, process steps which are difficult to carry out on an industrial scale, and the not always satisfactory yield of individual intermediate stages, this preparation process also raises industrial problems. It is, however, of extreme importance for the production of photoresists to have available an economical synthesis process for the radiation-sensitive components.
DD 263,982 discloses a preparation of 2-diazo-1-oxo-1,2-dihydronaphthalene derivatives, starting from 1,7-dihydroxynaphthalene derivatives. However, the 1,7-dihydroxynaphthalene-4-sulfonic acid used as the starting material for this purpose is not readily available, so that it is extremely expensive to carry out the overall process. Moreover, the diazotization of the amino intermediate is possible in acceptable quality only under defined conditions of pH and temperature and in the presence of heavy metal salts, and only in a low yield.
The esters and amides of 7-methoxy-1,2-naphthoquinone-2-diazide-4-sulfonic acid are, because of the shift of their absorption to longer wavelengths and because of their high reversal potential, outstandingly suitable for use in photoresist layers, which can be structured in the g-line (436 nm) and i-line (365 nm) regions and can be processed either positively or negatively.